1. Field of the Invention
The present invention relates to the production of a vastly improved particulate urea product, normally in granular or prill form, not only possessing eminently improved anticaking and hardness characteristics but also serving as a carrier for suspending agents used to suspend solids in the subsequent production of suspension fertilizers. The modus operandi of the instant invention follows the second and third embodiments discussed supra, to wit, directly or indirectly incorporating into the urea melt certain new, novel, and heretofore unknown additive materials. To be concise, the term unknown is used herein in the sense that said materials, although commonly available, have heretofore been unrecognized as either possessing (1) the desirable characteristics of imparting to the formed urea particles the improved physical characteristics, or (2) the viability of being utilized as built-in suspending agents when said urea particulates are subsequently used in producing fertilizer suspensions.
2. Description of the Prior Art
As mentioned supra, several investigators have discovered, taught, and disclosed a plethora of conditioing agents which may be added either directly to the anhydrous molten urea melt or indirectly thereto by means of incorporating same into the synthesis liquor before said melt is processed to the particulates formed therefrom to improve their anticaking characteristics of their nonfriable characteristics or in some instances both. These problems, as well as other attendent considerations for storage, handling, and application characteristics of granular/particulate urea, have heretofore been alleviated, to a significant degree, by the addition to the urea melt of low concentrations, e.g., 0.1 percent to 1.0 percent, by weight, of formaldehyde or compounds from the generic system of lignin chemicals known as lignosulfonates, which lignosulfonates are commonly produced as metal or ammonium salts of lignosulfonic acid, a by-product of the sulfite pulp paper process. Of particular interest from the practical aspects of this approach for methods employing the addition of formaldehyde and lignosulfonates, are those taught in the following patents:
______________________________________ U.S. Pat. No. Author Issue Date ______________________________________ 3,112,343 Allgeuer et al November 26, 1963 4,160,782 Van Hijfte et al July 10, 1979 4,204,053 Elstrom et al May 20, 1980 4,587,358 Blouin May 6, 1986 ______________________________________
Perusal of the above references, except for Blouin '358, reveals teachings of the formation of various concentrated solutions of a urea-formaldehyde reaction product(s) which are subsequently added in predetermined and desired amounts to the urea synthesis liquor, either before or after concentration thereof, or to the essentially anhydrous molten melt prior to ultimate formation of the desired particulate urea.
Although many of the problems associated with friability and caking of such formed particulate urea may be alleviated, as indicated above, to a significant degree by the addition of such relatively low concentrations of principally formaldehyde to either the urea synthesis liquor or the essentially anhydrous molten urea melt, modern day health and safety considerations under the genesis of environmental concerns have led to, or are presently leading to the close scrutiny of the many chemicals, organic as well as inorganic, utilized in the fertilizer-food chain. It is my understanding that formaldehyde may now be considered as a possible toxic and/or carcinogenic material by the U.S. Environmental Protection Agency (EPA). If so, such a designation could well lead to either the restriction or total prohibition of the use of formaldehyde in agriculture products, including perhaps its use as a conditioning agent in the preparation of urea for fertilizer or animal feed preparation purposes.
More recently, Blouin, '358 supra, assigned to the assignee of the present invention, has taught the use of, in combination with urea, calcium lignosulfonate (or other metal or ammonium lignosulfonates), homogeneously incorporated therewith and therein, as a vastly improved conditioning material for imparting to the resulting urea both superior anticaking and nonfriable chacteristics. Although this advance in the art by Blouin overcomes many of the disadvantages heretofore normally associated with the use of formaldehyde and derivatives thereof, it in itself may be fraught with cetain minor disadvantages, including the potential marketing acceptance problem that may ultimately prove to be associated with the distinctive brownish discoloration characteristic to materials produced by following his teachings. Aside from the problem of acceptance of brown urea by the farmer, urea utilized by the plastics industry in most instances, must be white in color, or substantially white, i.e., offwhite or cream as when the urea of the instant invention contains more than about 1.5 percent clay. Nevertheless, the teachings of Blouin appear, at this time, to represent a viable and highly desirable alternative to the state of the art upon which it improves. In addition, many of the procedures of producing and/or testing the materials of the instant invention closely parallel his teachings. Accordingly, for purposes of teaching, disclosing, and claiming the instant invention, the teachings and disclosure of Blouin, '358 supra, are herewith and hereby incorporated herein by means of this reference thereto.
It is verily believed that to those skilled in this art, who study the disclosure of the present invention, it will be appreciated that the practice of same overcomes a great multiplicity of the limitations and disadvantages of the various methods and/or means of the type presently found in the prior art and that the present invention results in a new, novel, and unique combination of certain selected features of the advances in the art set forth supra, albeit, with wholly unexpected results.